Train resonant car-body rocking detector system

ABSTRACT

A hydraulic sensor detects and registers the resonant rocking motion of a train car and activates the brake system to stop the train prior to possible derailment due to wheel &#39;&#39;&#39;&#39;rock-off&#39;&#39;&#39;&#39; from the track. A hydraulic input arm attached to the sideframe pressurizes fluid within the sensor mounted on the bolster. Pressure build-up within a specific time interval due to rock-off resonant oscillation causes a ram to extend from the sensor and crush a piezoelectric element. The resultant signal activates an electroexplosive brake line venting mechanism, puncturing and venting the brake line to decelerate the train and dissipate the resonant oscillation-mode energy to immediately stabilize the rock-off situation and then gradually reduce train speed to a stop.

United st:

Swaim 1 1 TRAIN RESONANT CAR-BODY ROCKING DETECTOR SYSTEM [75] Inventor: Frank H. Swaim, Silver Spring, Md.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington. DC.

[22] Filed: July 25. 1974 [211 Appl. No.1 491,983

1521 u.s.c1 246/169 R; 73/70; 188/110;

246/170; 340/261 51 1m.c1. B6lL 3/00 [58] Field of Search 246/16911. 170. 189. 190.

246/182 A. 303/21 A23-10/65, 261'. 92/5 R. 9, 10, 11. 12.73/70. 71.4; ZOO/61.08; 102/702 GA. 39 R; 89/1 B; 188/110;

[ 1 Nov. 25, 1975 3,858,392 1/1975 Evans 102/39 R FOREIGN PATENTS OR APPLICATIONS 715.739 l/1942 Germany 92/5 R Primary ExaminerTrygve M. Blix Assistant ExaminerReinhard J. Eisenzopf Attorney, Agent. or Firm-R. S. Sciascia; J. A. Cooke; F. K. Yee

[57] ABSTRACT A hydraulic sensor detects and registers the resonant rocking motion of a train car and activates the brake system to stop the train prior to possible derailment due to wheel rock-of from the track. A hydraulic input arm attached to the sideframe pressurizes fluid within the sensor mounted on the bolster. Pressure build-up within a specific time interval due to rock-off resonant oscillation causes a ram to extend from the sensor and crush a piezoelectric element. The resultant signal activates an electroexplosive brake line venting mechanism, puncturing and venting the brake line to decelerate the train and dissipate the resonant oscillation-mode energy to immediately stabilize the rock-off situation and then gradually reduce train speed to a stop.

25 Claims, 6 Drawing Figures US. Patent N0v.25, 1975 Sheet 1 of3 3,921,945

U.S. Patant Nov.25, 1975 Sheet20f3 3,921,945

U.S. Patent Nov. 25, 1975 Sheet3of3 3,921,945

TRAIN RESONANT CAR-BODY ROCKING DETECTOR SYSTEM BACKGROUND OF THE INVENTION The present invention relates generally to motion sensor systems and, more particularly, to a motion sensor system capable of recognizing certain types of oscillations common to railroad cars in an approaching derailment attitude.

Increases in freight car load capacity have been coupled with a desire to reduce tare weights by keeping car length to a minimum. As a result, there are a significant number of cars which have a relatively high center of gravity and a truck center distance close to the 39-foot standard rail joint spacing. When operated near the resulting resonant speed of 18 to 20 mph on a curved track, such cars may derail.

While the low speed at which such rock-off derailments typically occur would indicate that thier cost is probably equal to or less than that for equipmentcaused derailments as a class, total cost from this cause has been determined to be much higher, based upon recent data. Unlike other causes, this problem is largely confined to a segment of the freight car fleetperhaps 50,000 cars at the mostand the higher cost per affected car warrants greater consideration for a remedy.

Resonant rock-off has been studied rather extensively by railroads and suppliers, both analytically and experimentally. As a train moves along the track, railroad cars can acquire an oscillating attitude as a result of a combination of many factors, such as uneven load distribution, changes in the trains speed, shifts in payload, track alignment, strong cross wind, truck spring gradient, inherent structural dampening, periodic occurrence of staggered joints, truck spacing coincident with track length, and changes of center of gravity of loaded and unloaded cars. Such car-body rocking oscillations may become resonant and be amplified to a point which eventually leads to car derailment.

The motion prior to and during rock-off can be explained by considering the car body mounting on the truck. The car body pivots on the truck bolster, with the load of the car-body being transmitted to the truck through several compression springs at each end of the bolster. As ocillation of the car body takes place, the bolster, being spring loaded, causes greater compression of the springs on the dip side, while on the lifting side the springs become extended due to diminishing load during the rocking action, similar to a see-saw type motion. The critical point in incipient resonant rock-off occurs when the truck springs on the high side of the car become completely unloaded. There is then no longer any force holding down the unsprung masses, i.e., the wheels, sideframe and half of the axle weight, except their own weight. The leverage of the high load on the low side of the truck acting on the overhanging journals is sufficient to lift the wheels the height of the wheel flange in a time much shorter than the period of the resonant rocking motion. If the car is on curved track, at the time of actual wheel lift, derailment is inevitable.

Application of special friction damping devices, such as stabilizers or snubbers, either between the truck sideframe and the car body or the sideframe and bolster, has been effective in reducing resonant rock-off in susceptible cars. However, these damping devices are prone to failure. In the event of, or as insurance against,

such'failures, it is desirable that means be provided to detect resonant rocking-mode oscillations and effect positive action prior to derailment. Any effective antiderailment action will have to be initiated prior to complete unloading of the springs. Otherwise, the flange will beatop the rail long before the car body motion again puts load on the wheel. This means that only a few seconds warning is available before rock-off.

Since the positive action that could be taken in this time frame must be completely automatic, a service brake application initiated at the car in question or the triggering of some other emergency auxiliary damping device on its suspension are the only system primary outputs that appear possibly effective. The latter does not appear economically promising vis-a-vis applying a more reliable, e.g., multi-element, redundant, stabilization system in the first place. Assuming a brake application, the mass of the car body will press the truck bolsters against the sideframes as the braking force decelerates the car. This will create friction and dissipate rocking-mode energy. A brake application will thus stabilize the situation immediately and then gradually reduce train speed to the pointwhere the resonant condition no longer governs.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a new and improved sensor system that can recongize and register resonant car body rocking motion.

Another object of the present invention is to provide a new and improved sensor system that can recognize and register resonant car body rocking motion characteristic of an incipient railroad car derailment.

Another object of the invention is to provide a new and improved sensor system that will only recognize and register resonant car body rocking motion but will not register single, short-stroke oscillations.

Still another object of the invention is the provision of a new and improved sensor system that can recognize and register a series of resonant car body motion characteristic of incipient railroad car derailment.

A further object of the present invention is to provide a new and improved sensor system that can recognize and register resonant car body rocking motion but will not register such motion if not produced within a specific time period.

A still further object of the invention is to provide a new and improved sensor system that can recognize and register resonant car body rocking motion characteristic of incipient railroad car derailment and produce an anti-derailment output signal.

Yet still another object of the present invention is the provision of a new and improved sensor system that can recognize and register resonant car body rocking motion characteristic of incipient railroad car derailment and activate the brake system to stop the car.

Briefly, these and other objects of the present invention are attained in a resonant oscillation detector/register and brake actuation system comprising ahydraulic sensor which detects and registers the resonant rocking motion of a train car in an approaching derailment attitude and activates the brake system to stop the train. Pressure within the sensor is generated by an actuating arm coupling the sideframe to the sensor mounted on the bolster. Rapid pressure increases which exceed the built-in pressure relief of the sensor causes a center ram to become effectively extended, crushing a piezoelectric element attached to the side- 3 frame to produce an electric signal. An explosivelyactivated bellows motor actuator within a brake line venting mechanism is triggered by the signal, causing a diaphragm cutter to vent the trains brake line and stop the train.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the invention and many of the attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a partial side view of a train truck embodying the motion sensor and register mechanism of the present invention;

FIG. 2 is a more detailed showing of the sensor of FIG. 1;

FIG. 3 is a partially-sectioned plan view of a train car embodying the system of the present invention;

FIG. 4 is an elevation view of the train car of FIG. 3;

FIG. 5 is a partially-sectioned view of the brake line venting mechanism; and

FIG. 6 shows the bellows actuator of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 wherein the resonant car body rocking motion sensor, generally designated by the numeral 10, is shown mounted on the bolster 12 with actuator arm 14 attached to the sideframe 16.

Details of the sensor 10, which can be more clearly seen from FIG. 2, comprises a housing 18 provided with a plurality of interconnected internal cavities for a hydraulic fluid l9. Actuator arm 14 is attached at one end to a piston 20 which is reciprocally received within fluid chamber 22. Piston 20 is provided with suitable sealing means 21 known in the art to prevent fluid bypass. Adjacent to chamber 22 and integral with housing 18 is a fluidreservoir 24. An orifice 26 is provided in the partition 28 separating chamber 22 and reservoir 24 to permit fluid flow therebetween. Reservoir 24 is centrally provided with a cylindrical chamber 30, defined by the cylindrical wall 32, in which is reciprocally positioned a center ram 34 attached to a ram arm 36 extending through the upper surface of housing 18. A spring 38 biases the center ram 34 downwardly. The lower portion of chamber 30 forms a pressure chamber 40 which is in fluid communication with chamber 22 via an interconnecting passage 42. A spring-loaded, oneway ball valve 44 closes an orifice 46 provided approximate the base of chamber 22. Pressure chamber 40 is in fluid communication with fluid reservoir 24 by means of a flow control valve 48 controlling the fluid flow through interconnecting passage 50 and an inlet orifice 52 provided in the base of reservoir 24. In its lowermost position, center ram 34 rests upon a pin 54 projecting from the base of pressure chamber 40. An annular seal 58 prevents fluid by-pass from chamber 40.

In the operative position shown in FIGS. 1 and 2, the sensor is suitably mounted on the end of bolster 12 with the actuator arm 14 appropriately attached to the sideframe 16 of the railroad car truck. When the railroad car begins to oscillate the bolster begins to seesaw with respect to the sideframe. Each oscillation; or movement between the bolster and sideframe, represents a stroke on the hydraulic mechanism, i.e., actuator arm 14 and piston 20, of the sensor. Each stroke causes a downward movement of the actuator arm 14; compresses the fluid in chamber 22; forces the prerssurized fluid through the orifice 46, past the ball valve 44 and into pressure chamber 40 through passage 42; and causes ram 34 to rise against the force of spring 38. At the same time pressure relief is occurring through the flow control valve 48 as the fluid is returned to reservoir 24 under the combined influence of the mass of ram 34 and the force of spring 38. This dynamic flow continues as long as pressure remains in the sensor. A continuous oscillating motion causes a continuous pressure build up in chamber 40, and since the flow through valve 48 remains constant even as the oscillation frequency increases, the increased pressure in chamber 40 not relieved through valve 48 causes ram 34 and ram arm 36 to rise from the lowermost position of FIG. 2. Thus a continued number of strokes within a limited time interval will close the gap between the top of ram arm 36 and sideframe 16. When this gap is completely closed, ram arm 36 jams against the sideframe and crushes the piezoeletric element 56. The relatively high-voltage, short-pulse-duration current generated by element 56 is conducted to bellows motor actuator 84 (see FIG. 6) by means of the shielded conductor 60. The operation of the actuator 84 to stop the train will be considered more fully below.

While FIG. 2 shows the piezoelectric element 56 mounted within a recess on sideframe 16, the element can also be attached to the end of ram arm 36. In either position, the operation is similar. The location of FIG. 2 provides a degree of environmental protection for element 56, and in this respect is the preferred location.

In the foregoing description of sensor operation the stroke-time cycle is sufficient to effectively extend the ram arm 36 against the piezoelectric element 56. When the sequence of sensor functions does not match the time cycle, ram arm 36 does not become effectively extended. The time cycle is regulated by the pressure relief through flow control valve 48 and is depended upon car weight, loaded and unloaded. Thus if the time lag between strokes of the actuator arm 14 is too great, the pressure relief through valve 48 is greater than the pressure generated within chamber 40 and ram arm 36 experiences no displacement. Conversely, if the actuator input is greater than the pressure relief, the ram arm will rise faster to its effective, extended position, activating the detector system to stop the train. In this manner short and/or infrequent strokes of the actuator arm will not activate the brake system. Inherent in the design of the sensor is the capability to recognize a long, full stroke, such as occurs due to a broken track, to stop the train.

FIGS. 3 and 4 show the plan view and elevation view, respectively, of a train car 64 provided with the brake actuation subsystem of the present invention. The motion sensors 10, each with its associated piezoelectric element 56, are electrically connected by a shielded conductor system 60, such as sheathed or armored cable, to the brake line venting mechanism 76. The trains brake line 62 extend the length of car 64 and terminate in end couplings 66. Connected to the train line 62 are the brake valve 68, brake cylinder and brake reservoir 72, elements common to a trains brake system and known in the art.

While FIGS. 3 and 4 show four motion sensors 10, one on each bolster, only one sensor is necessary to be fully effective in detecting train car-body resonant rocking. The use of multiple sensors, as shown in FIGS. 3 and 4, is suitable for incorporation into a total train derailment prevention system, including the roller bearing overheating sensor system disclosed more fully in the copending application Ser. No. 495,478 of J.H. Armstrong and RC. Kluge and the local derailment sensor system disclosed in copending application Ser. No. 495,480 of J.H. Armstrong and W.W. Wassmann, both filed on Aug. 7, 1974. These copending applications also describe more fully the piezoelectric element 56 and the thermal battery, which may be used in place of the piezoelectric element. Both the piezoelectric element and the thermal battery are widely used in ordnance hardware and are known to those skilled in the art.

Positioned on the brake pipe 74 joining the brake valve 68 to the train line 62 is the brake line venting mechanism 76, shown more fully in FIG. 5. The venting mechanism includes shield 78 surrounding a diaphragm cutter having a cylindrical housing 82; an explosivelydriven bellows motor actuator 84 connected to the electrical conductors 60 positioned at one end of housing 82; a slidably-mounted cutter 86 disposed adjacent the actuator 84; a shearable diaphragm 88 positioned adjacent the other end of housing 82 to separate the housing from the internal passage of brake pipe 74; an annular passage 90 provided in the housing 82 to permit passage of air from the brake pipe 74 after diaphragm rupture; and a calibrated venting orifice structure 92 to vent the released air. Also visible in FIG. is the dirt chamber 94 and the cut-out cock 96, elements common to train brake systems. The shield 78 around the diaphragm cutter, as well as the shielding around conductor 60, serves to prevent interference from stray electromagnetic radiation and to provide mechanical protection against the severe enviroment existing beneath the train car. The diaphragm cutter may be similar to that disclosed in copending application Ser. No. 465,400, filed Apr. 29, 1974, and the explosive-type cutter actuator described therein may be used in place of the bellows motor actuator 84.

Details of the bridge-wire bellows motor actuator 84 may be seen in FIG. 6 wherein the wires 100 of the shielded conductor 60 are positioned against a propellant 102 contained in cup 104, the ends of wires 100 being joined by a fine bridge wire 106 embedded in the propellant. Wires 100 are suitably insulated with insulating material 108, and cup 104 is sealed with a plug 110 of glass, plastic or other suitable material. Bellows 112 is pleated from suitable malleable, ductible metal, such as copper, with the forward end formed into a blunt nose 114 and the edge of the aft, open end crimped over the seal plug 110. Approximate this open edge, the bellows 112 is provided with an outwardlyextending ridge 116, which receives a similarly-shaped ridge formed on the propellant cup 104 to properly position the cup.

The operation of the bellows motor actuator and the venting mechanism 76 can be readily seen from the foregoing description. Briefly, the propellant 102 is ignited by the signal generated by piezoelectric element 56, as set forth above, the expanding gases forcibly extending the bellows 112, causing the blunt nose 114 to contact and displace cutter 86, which in turn severs diaphragm 88 to release the air from brake pipe 74, thus slowing and eventually stopping thetrain. The escaping air flows out through passage and the venting orifice 92. As the air flows through orifice 92, a distinct, audible sound is produced to help the train crew locate'the car which has been braked and to determine what possible derailment condition has actuated the system. This permits remedial action prior to any actual derailment. Additionally, the actuation of the brake system can be monitored from a central location, such as the engine cab.

Bellows 112 is sufficiently rigid after expansion to prevent cutter'86 from being forced by air pressure back through the ruptured diaphragm and possibly obstructing the flow. To further assure free air flow, cutter 86 may be hollow with an opening 118 therein to permit unobstructed flow between brake pipe 74 an annular passage 90.

Obviously, numerous modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practice otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A motion sensor for detecting and registering motion to produce an output signal only for certain types of periodic motion comprising:

hydraulic fluid containment means;

a displaceable input means responsive to motion for applying pressure to the fluid in a first chamber of said containment means;

a displaceable extensible member in a second chamber of said containment means, said first and said second chambers in fluid communication;

flow control means to regulate fluid flow between said first and said second chambers; and

pressure relief means in said second chamber to regulate fluid flow from said second chamber,

whereby displacement of said input means pressurizes the fluid in said first chamber to displace said extensible member only when the input pressure exceeds the pressure relief from said second chamber.

2. The motion sensor of claim 1 further comprising a fluid reservoir in fluid communication with said first and said second chambers.

3. The motion sensor of claim 2 wherein said flow control means comprises a one-way valve.

4. The motion sensor of claim 3 wherein said oneway valve comprises a spring-loaded ball valve.

5. The motion sensor of claim 3 wherein said pressure relief means comprises an adjustable flow control valve.

6. The motion sensor of claim 5 wherein said displaceable input means comprises:

an elongated actuating arm connectable to the source of motion; and

a piston attached to said actuating arm and reciprocable in said first chamber.

7. The motion sensor of claim 6 wherein said extensible member comprises:

an elongated arm extendable from said containment means;

a ram piston connected to said elongated arm and reciprocable in said second chamber; and

a spring biasing said ram piston downwardly.

8. The motion sensor of claim 7 further comprising an electrical signal producing means cooperating with said elongated arm to produce an output signal upon a predetermined displacement of said elongated arm.

9. The motion sensor of claim 8 wherein said electrical producing means comprises a piezoelectric element positioned on the source of motion and is crushed by the predetermined displacement of said elongated arm.

10. The motion sensor of claim further comprising an electrical signal producing means cooperating with said extensible member to produce an output signal upon a predetermined displacement of said extensible member.

11. The motion sensor of claim 10 wherein said electrical signal producing means comprises a piezoelectric element crushed by the predetermined displacement of said extensible member.

12. In combination with a train car amotion sensor and actuator system for detecting and registering critical periodic motion and actuating the train brake system comprising:

a hydraulic motion sensor responsive to periodic motion of the train; signal producing means cooperating with said motion sensor to produce an output signal; and

electroexplosive means responsive to said output signal to vent the brake lines on said train car to stop said train car.

13. The combination of claim 12 wherein said electroexplosive means comprises a explosively-activated diaphragm cutter.

14. The combination of claim 13 wherein said signal producing means comprises a piezoelectric element crushed by said motion sensor to produce an electric signal.

15. The combination of claim 14 further comprising conductor means connecting said piezoelectric element and said diaphragm cutter.

16. The combination of claim 12 wherein said hydraulic motion sensor comprises:

a displaceable input means coupled to said train car for applying pressure to fluid in said sensor;

flow control means to relieve the pressure in said senson, and

a displaceable extensible member responsive'to the pressurized fluid and displaced from said sensor only when the input pressure exceeds the pressure relief.

17. The combination of claim 16 wherein said mot-ion sensor comprises:

containment means for hydraulic fluid;

a first chamber in said containment means to receive said displaceable input means:

a second chamber in fluid communication with said first chamber to receive said displaceable extensible member; and

fluid flow control means between said first and said second chamber to regulate the flow between said first and said second chambers.

18. The combination of claim 17 wherein said fluid flow control means comprises a one-way flow valve and said pressure relief means comprises an adjustable flow valve to regulate fluid flow from said second chamber.

19. The combination of claim 18 wherein said motion sensor further comprises a fluid reservoir in fluid communication with said first and said second chambers.

20. The combination of claim 19 wherein said displaceable input means comprises:

an elongated actuating arm attached to said train car;

and

a piston attached to said actuating arm and reciprocable in said first chamber.

21, The combination of claim 20 wherein said extensible member comprises:

an elongated arm extendable from said containment means;

a ram piston connected to said elongated arm and reciprocable in said second chamber; and

a spring biasing said rarn piston downwardly.

22. The combination of claim 21 wherein said signal producing means comprises a piezoelectric element mounted on said train car and crushed by said extendable elongated arm to produce an electric signal.

23. The combination of claim 22 wherein said electro-explosive means comprises an explosively-actuated diaphragm cutter to puncture and vent the train brake line.

24. The combination of claim 23 wherein said diaphragm cutter is actuated by an explosively-extended bellows motor.

25. The combination of claim 24 further comprising a calibrated venting means connected to said diaphragm cutter capable of producing an audible signal upon brake line venting. 

1. A motion sensor for detecting and registering motion to produce an output signal only for certain types of periodic motion comprising: hydraulic fluid containment means; a displaceable input means responsive to motion for applying pressure to the fluid in a first chamber of said containment means; a displaceable extensible member in a second chamber of said containment means, said first and said second chambers in fluid communication; flow control means to regulate fluid flow between said first and said second chambers; and pressure relief means in said second chamber to regulate fluid flow from said second chamber, whereby displacement of said input means pressurizes the fluid in said first chamber to displace said extensible member only when the input pressure exceeds the pressure relief from said second chamber.
 2. The motion sensor of claim 1 further comprising a fluid reservoir in fluid communication with said first and said second chambers.
 3. The motion sensor of claim 2 wherein said flow control means comprises a one-way valve.
 4. The motion sensor of claim 3 wherein said one-way valve comprises a spring-loaded ball valve.
 5. The motion sensor of claim 3 wherein said pressure relief means comprises an adjustable flow control valve.
 6. The motion sensor of claim 5 wherein said displaceable input means comprises: an elongated actuating arm connectable to the source of motion; and a piston attached to said actuating arm and reciprocable in said first chamber.
 7. The motion sensor of claim 6 wherein said extensible member comprises: an elongated arm extendable from said containment means; a ram piston connected to said elongated arm and reciprocable in said second chamber; and a spring biasing said ram piston downwardly.
 8. The motion sensor of claim 7 further comprising an electrical signal producing means cooperating with said elongated arm to produce an output signal upon a predetermined displacement of said elongated arm.
 9. The motion sensor of claim 8 wherein said electrical producing means comprises a piezoelectric element positioned on the source of motion and is crushed by the predetermined displacement of said elongated arm.
 10. The motion sensor of claim 5 further comprising an electrical signal producing means cooperating with said extensible member to produce an output signal upon a predetermined displacement of said extensible member.
 11. The motion sensor of claim 10 wherein said electrical signal producing means comprises a piezoelectric element crushed by the predetermined displacement of said extensible member.
 12. In combination with a train car a motion sensor and actuator system for detecting and registering critical periodic motion and actuating the train brake system comprising: a hydraulic motion sensor responsive to periodic motion of the train; signal producing means cooperating with said motion sensor to produce an output signal; and electroexplosive means responsive to said output signal to vent the brake lines on said train car to stop said train car.
 13. The combination of claim 12 wherein said electroexplosive means comprises a explosively-activated diaphragm cutter.
 14. The combination of claim 13 wherein said signal producing means comprises a piezoelectric element crushed by said motion sensor to produce an electric signal.
 15. The combination of claim 14 further comprising conductor means connecting said piezoelectric element and said diaphragm cutter.
 16. The combination of claim 12 wherein said hydraulic motion sensor comprises: a displaceable input means coupled to said train car for applyinG pressure to fluid in said sensor; flow control means to relieve the pressure in said sensor; and a displaceable extensible member responsive to the pressurized fluid and displaced from said sensor only when the input pressure exceeds the pressure relief.
 17. The combination of claim 16 wherein said motion sensor comprises: containment means for hydraulic fluid; a first chamber in said containment means to receive said displaceable input means: a second chamber in fluid communication with said first chamber to receive said displaceable extensible member; and fluid flow control means between said first and said second chamber to regulate the flow between said first and said second chambers.
 18. The combination of claim 17 wherein said fluid flow control means comprises a one-way flow valve and said pressure relief means comprises an adjustable flow valve to regulate fluid flow from said second chamber.
 19. The combination of claim 18 wherein said motion sensor further comprises a fluid reservoir in fluid communication with said first and said second chambers.
 20. The combination of claim 19 wherein said displaceable input means comprises: an elongated actuating arm attached to said train car; and a piston attached to said actuating arm and reciprocable in said first chamber.
 21. The combination of claim 20 wherein said extensible member comprises: an elongated arm extendable from said containment means; a ram piston connected to said elongated arm and reciprocable in said second chamber; and a spring biasing said ram piston downwardly.
 22. The combination of claim 21 wherein said signal producing means comprises a piezoelectric element mounted on said train car and crushed by said extendable elongated arm to produce an electric signal.
 23. The combination of claim 22 wherein said electro-explosive means comprises an explosively-actuated diaphragm cutter to puncture and vent the train brake line.
 24. The combination of claim 23 wherein said diaphragm cutter is actuated by an explosively-extended bellows motor.
 25. The combination of claim 24 further comprising a calibrated venting means connected to said diaphragm cutter capable of producing an audible signal upon brake line venting. 